This invention relates generally to an attachment for securing pressure sensitive controls to systems which operate under high or low pressures, or both, and more particularly, to a threadless coupling for securing pressure sensitive switches to such systems.
Generally, in systems which operate under high or low pressures, or both, pressure sensitive controls responsive to predetermined high or low pressures are utilized to enhance system performance. Such controls also increase the system operating life by controlling the pressure within the system to be within a predetermined range. For example, in automotive air conditioning systems which include a compressor extremely high pressures can adversely affect the operating life of the compressor and other components within the system. To prevent the pressures within such systems from reaching such high magnitudes, a pressure sensitive control responds to a predetermined high pressure by, for example, de-energizing the compressor. When the pressure within the system returns to a predetermined safe level, the pressure sensitive control responds by energizing the compressor.
Many known pressure sensitive controls have been used with such pressurized systems. One example of such a control is described in Hogue et al., U.S. Pat. No. 5,300,741, which is assigned to the present assignee. Known pressure sensitive controls such as the control described in Hogue et al. include a snap-disc normally biased in a first position which "snaps" to a second position in response to a predetermined pressure within a pressurized system. A movable contact and a stationary contact are included within the control. The movable contact moves in response to the movement of the snap-disc.
In a typical application, the pressure sensitive control is coupled between an energy source and a compressor clutch of the pressurized system. Under normal conditions, the moveable contact engages the stationary contact in a circuit-making condition and the compressor is energized. If the pressure within the system exceeds a predetermined level, the snap-disc "snaps" to the second position causing the moveable contact to move away from the stationary contact into a circuit-breaking condition. In the circuit-breaking condition, energy to the compressor is cut off thereby preventing the pressure within the system from increasing. When the pressure within the system returns to a predetermined safe level, the snap-disc returns to its normal position, i.e., the first position, the movable contact again engages the stationary contact, and the compressor is energized.
In addition to controlling energization of the compressor motor, such switches also are used to control compressor cycling and cooling fans and low pressure cut-outs. For example, with respect to low pressure cut outs, when the system pressure falls below a predetermined level, the control causes the system compressor to be de-energized.
Known pressure sensitive controls are attached to pressurized systems by threaded couplings. The manufacture of threaded components for the couplings involves cutting, rolling, tapping or, in the case of plastic parts, molding thread details in the parts. These operations are expensive, regardless of the method or type of material used. The assembly expense of threaded components is also high because proper mating of threaded components requires special tooling for tightening the components to a specific torque. The tooling and torque requirements also increase the time required for assembly and disassembly.
In addition to the time and expense associated with threaded members, problems can arise during assembly such as cross-threading or over stressing. Compensation for over stressing can been achieved through the use of metal components due to their increased strength over plastic components. However, the use of metal components results in higher manufacturing expense.
In an attempt to overcome the problems with threaded couplings, threadless couplings have been used in some applications. Various known threadless couplings are illustrated in FIGS. 1-3. Specifically, FIG. 1 illustrates a coupling 20 for an air conditioning system including first and second tubular members 22 and 24. First tubular member 22 includes a first passageway 26, and two o-rings 28, 29 are inserted in annular grooves formed in outer surface 30 of such member 22. First tubular member 22 also has a spring retaining housing 32 with a spring 34 therein. Second tubular member 24 includes a second passageway 36 and, at its mating end, forms a lip 38.
To engage first and second tubular members 22 and 24, lip 38 of second member 24 is inserted into housing 32 and forced under spring 34. Spring 34 retains lip 38 within housing 32. A snap ring 40 may be fit over spring 34 and into engagement with housing 32.
Another known coupling 50 is illustrated in FIG. 2. Coupling 50 may be used in connection with speedometer cable for an automobile. Coupling 50 includes a connector 52 which receives a mating member 54 attached to one end of the speedometer cable. Connector 52 includes a passageway 56. One end of passageway 56 is enlarged. A slot 60 is formed in connector 52 and a substantially u-shaped resilient wire retaining member 62 is inserted through slot 60. Mating member 54 has an annular flange 64 formed at an intermediate location along its length.
To engage mating member 54 with connector 52, mating member 54 is inserted into passageway 56. Flange 64 is inserted through resilient retaining member 62, which expands to allow flange 64 pass therethrough. Once flange 64 is inserted through member 62, member 62 contracts to its normal configuration. Cooperation of flange 64 and retaining member 62 maintains engagement between mating member 54 and connector 52.
A coupling 70 for an automobile fuel filter is illustrated in FIG. 3. A connector 72 is engaged to tube 74 having a passageway 76. Specifically, ridges 78 are formed on a tubular extension 80 of connector 72, and tube 74 is pushed over ridges 78. Connector 72 also includes an opening 82 and a passageway 84 sized to receive a tubular extension 86 of a fuel filter. Two o-rings 88, 89 are mounted in grooves formed in passageway 84. An annular flange 90 is formed at an intermediate location along tubular extension 86. A plastic clip 92 is inserted through openings 94 formed in connector 72. Clip 92 cooperates with flange 90 to maintain tubular extension 86 and connector 72 in engagement.
Although such threadless couplings are useful in some applications, there still exists a need for a threadless coupling that can be utilized in both high and low pressure controls and in connection with fluid flow valves, such as a Schrader valve, if desired. A Schrader valve, for example, allows replacement of a switch in a pressurized system without having to evacuate and re-charge the system. Further, there exists a need for such a threadless coupling that is inexpensive to manufacture and is easy to assemble and disassemble.
Accordingly, it is desirable and advantageous to provide a coupling for pressure sensitive controls that does not require the use of threaded members. It also is desirable and advantageous to provide a coupling for both high and low pressure sensitive controls that is inexpensive to manufacture and simple to assemble and disassemble.